Correct Use of Personal Pronouns - Grammar short lessons

A personal pronoun must be of the same number, gender and person as the noun it stands for.
John is a good boy. He loves and respects his parents and teachers. (Here the pronoun he is
of the same number, gender and person as the noun John.)
Alice is my sister. She lives abroad. (Here the pronoun she is of the same number, gender and
person as the noun Alice.)
The students worked hard. Their teacher praised them. (Here the plural pronoun them is of
the same number, gender and person as the plural noun students.)...